1. Field of the Invention
The present invention relates to an electroacoustic transducer which transduces an electric signal to a sound.
2. Description of the Related Art
Japanese Patent Publication No. Hei.08-6558 discloses an electroacoustic transducer that comprises a case and a pole piece inside the case. The pole piece includes a base and a core integrally fixed to each other. A coil is disposed around the core. A magnet is disposed around the coil with a space from the coil. The coil is provided by directly winding a conductive wire around the core, or by mounting a prewound coil on the core.
However, the electroacoustic transducer faces such a problem that the conductive wire may get in touch with the base made of metal and causes friction therewith, when the conductive wire is wound around the core or a prewound coil is mounted, or when the end portions of the conductive wire forming the core are drawn out to be electrically connected to terminal parts. Consequently, the conductive wire, specifically an insulating layer thereof, maybe damaged. The damaged conductive wire may cause a short circuit when it comes into contact with the metallic parts of the base and so on. Such a short circuit may result in decrease in reliability and durability of the electroacoustic transducer.
The present invention has been made in view of the above described drawback, and an object of the invention is to provide an electroacoustic transducer which can prevent a damage of a conductive wire composing a coil, so that decrease in reliability and durability hardly occurs.
According to the invention, there is provided an electroacoustic transducer comprising:
a pole piece including a core and a base;
a coil composed of a winding of a conductive wire and disposed around the core;
a magnet disposed around the coil;
a guide part for preventing the conductive wire from getting in touch with the base, the guide part being formed of material having a lower hardness than the base.
In the electroacoustic transducer according to the invention, such an occurrence that the conductive wire drawn from the coil may get in touch with the base can be avoided by a presence of the guide part which is made of the material having a lower hardness than the base, and accordingly, the conductive wire (a coating layer thereof) can be prevented from being damaged through a contact with the base. As the results, there is no such a risk that the metallic parts of the base and so on may come into contact with the damaged conductive wire and a short circuit may occur or the conductive wire may be broken. Decrease in reliability and durability of the electroacoustic transducer can be thus restrained.
Preferably, the electroacoustic transducer further comprises a case includes an upper case, and a lower case having a coil terminal to which the end portion of the conductive wire is electrically connected,
the base is placed on the lower case, and
the guide part is provided on the lower case and has a height equal to or higher than a top surface of the base.
In this manner, a structure of the guide part which can prevent the conductive wire from getting in touch with the base can be realized in a simple form and at a low cost.
Preferably, the case is formed of resin material, and the guide part is provided on the lower case by being integrally formed therewith. Because the case is formed of resin material, and the guide part is integrally formed on the lower case, in this manner, there is no need of newly providing a component for constituting the guide part, nor an additional step of providing the guide part on the lower case by adhesion or the like. As the results, the guide part can be provided on the lower case in a simple form and at a low cost.
Further, the base is preferably formed with a cut out which can be engaged with the guide part. Since there is formed, in the base, the cut out which can be engaged with the guide part, positioning of the base can be reliably conducted. Moreover, by forming the cut out in the base, a capacity of the base can be decreased. As the results, a capacity of a rear space in the electroacoustic transducer can be increased, and its sound pressure performance, especially, the sound pressure performance in a bass range can be enhanced.